Keratin (SCH2CH(NH2)COOH) is a fibrous protein that is composed of several units of the amino acid cystein and is responsible for providing protection to the external layers of the skin, hair and fingernails.
The epidermis, the external layer of the skin, is divided in four portions. The outermost one, which is known as stratum corneum, is made up of dead cells and keratin and constitutes the major physical barrier to the penetration of topical use compositions. In general, hair and fingernails are also composed of keratin.
The human hair, for example, has a complex structure that consists of three distinct morphological components, its primary element being the keratin that corresponds to at least 65% of the hair fiber. The central core of the fiber is known as medulla. It is surrounded by the cortex, a layer composed of keratinized cells, that provide every fiber with mechanical strength. The outermost layer is the cuticle, a fine layer of juxtaposed keratinized scales that acts as a protective barrier.
The amino acid cystein that is present all over the extension of the keratin polymer, contains sulfur. Through oxidation, two molecules of cystein can provide strong disulfide links and, thus, bind adjacent keratin polymers. Such cystein links contribute to the strength of the hair and are responsible for its durability and resistance.
Daily, the keratinous substrata, mainly the hair, are exposed to several kinds of stress. Some of them are induced by environmental factors, such as UVA and UVB radiation, or by mechanical treatments using combs, brushes, heat drying devices, among others. Also, there is the stress caused by chemical processes in the form of dyes, permanents, smoothing and discoloration. These processes not only destroy the cystein links (disulfide bridges), but also cause the loss of proteins, loss of hydration, premature aging, hardness, fragility, rupture of fibers, and the like (as per “Chemical and Physical Behavior of Human Hair”, Fourth Edition, Clarence R. Robbins).
Compositions for the care of keratinous substrate are known, but such compositions are not capable of providing, simultaneously, superficial as well as deep care to said substrata. A number of patent documents disclosing care compositions of keratinous substrata are given below, some formulated in the lamellar phase, but they neither indicate nor suggest simultaneous superficial and deep care.
The international patent application WO99/44564 discloses a composition in the form of a micro-emulsion for treating keratin fibers that comprises UV absorbers. Application WO93/15709 discloses a prophylactic composition containing an oleophilic liquid vehicle that promotes the diffusion of reagents in keratinous materials.
Application WO99/62462 discloses a composition for the repair and prevention of damage to the hair fiber that comprises a dispersion of multilamellar vesicles formed as a mixture of cholesterol and amino acids, and fatty acid.
U.S. Pat. No. 6,342,238 discloses a composition for stabilizing oxidation sensitive compounds that comprises an oily phase in a glycerol phase, and a non-ionic surfactant, said compound being dispersed in the glycerol phase.
Most of the available lamellar compositions comprise water, for example forming structures of the oil in water type, which makes it difficult to attain deep care, resulting only in superficial care of keratinous substrata.
The compositions that provide deep care of keratinous substrata are still more difficult to be obtained, mainly for keratinic fibers, including hair, body hair, eyebrows, eyelashes, mustache, beard, among others.
Some compositions that act as a vehicle for the transdermal administration of actives also can be found, but such compositions act as a vehicle in the transport of actives through the whole extension of the skin and are not suitable for the superficial treatment thereof.
For example, the international patent application WO02/24152 describes a pharmaceutical or cosmetic composition in the form of a micro-emulsion of vegetable oil in glycerin that comprises at least one emulsifier selected among glycosides, sucrose esters or sorbitan and a bioactive component of a hydrophobic moiety. The composition makes it easier for the bioactive agent to penetrate the stratum corneum and dermis and its diffusion in the blood stream, resulting in a systemic effect via transdermal route.
Thus, there remains the need of a composition that makes it possible to attain the simultaneous superficial and deep repair of damages suffered by keratinous substrata.